Antigen recognition (6) Flashcards
What does the immune system recognise?
- Non self molecules (antigens)
2. Danger
Where are danger signals generated from?
From injured tissues endogenously.
Who came up with the danger hypothesis in 1994?
Matzinger.
What happens after primary contact with an antigen?
An innate and a weak adaptive response
What does secondary contact with an antigen result in?
An enhanced adaptive response resulting in immunological memory.
What leucocytes are involved in the innate response?
Phagocytes, NK cells.
What leucocytes are involved in the adaptive response?
B and T lymphocytes.
What soluble factors are involved in the innate response?
Lysosyme, complement and interferons.
What soluble factors are involved in the adaptive response?
Antibodies.
What is clonal selection?
When T and B lymphocytes with the correct receptor undergo……..
What can persist after an infection?
T and B memory cells.
Who came up with the Clonal Selection Hypothesis in 1958?
Macfarlane Burnett.
What does the clonal selection hypothesis say happens early on in development?
Lymphocytes that recognise ‘self’ are detected early in development.
What happens in the clonal selection hypothesis after lymphocytes that recognise ‘self’ are deleted?
The lymphocyte with the appropriate receptor expand to produce both plasma cells and memory cells. These plasma cells go on to produce antibody.
What happens in the primary lymphoid tissue?
Lymphocytes reach maturity.
What happens in the secondary lymphoid tissue?
Mature lymphocytes are stimulated by antigen.
What happens in the draining lymph node?
Activation of the adaptive immune response?
How does the bacterial component reach the lymph node and how?
Through the afferent lymphatic vessel via dendritic cells.
What activates the T cells in the lymph node?
Dendritic cells.
How do naive T/B cells reach the lymph node?
Through the artery.
What leaves the lymph node through the efferent lymphatic vessel?
Antibodies and effector T cells.
What is an epitope?
The molecular shape an antibody recognizes on an antigen.
What two forms of antibody (immunogloblins) are there?
- Integral membrane proteins on B lymphocytes.
2. Soluble proteins secreted by plasma cells.
What are antigen receptors?
Antibodies existing on integral membrane proteins on B lymphocytes.
What are antigen eliminators?
Antibodies existing as soluble proteins secreted by plasma cells.
Antibodies structure reflect their dual roles. What are these two roles?
1, Antigen recognition.
2. Antigen elimination.
What part of the antibody is used for antigen recognition?
Fab regions.
What part of the antibody is used for antigen elimination?
Fc region.
Why can the Fab regions be involved in antigen recognition?
They are variable in sequence so can bind antigens specifically.
Why can the Fc regions be involved in antigen elimination?
They are constant in sequence so can bind to Fc receptors on various immune system cells.
Fc regions on antibodies can bind to Fc receptors on immune system cells in order to undergo antigen elimination. What cells have these receptors?
Phagocytes and NK cells.
How heavy is the light chain?
25kD
How heavy is the heavy chain?
50kD
How heavy is an immuogloblin?
150kd.
Only the Fab fragment is commonly used in research. True or false?
False, the Fc fragment can be used also.
What antibody fragments are produced by papain proteolytic cleavage?
Fab, Fab, Fc.
What antibody fragments are produced by pepsin proteolytic cleavage?
F(ab’)2
What do the immunoglobulin classes differ in?
Amino acid sequences of their heavy chains.
What is the other name for IgG?
γ
What is the other name for IgM?
μ
What is the other name for IgA?
α
What is the other name for IgD?
δ
What is the other name for IgE?
ε
What is the main role of IgG?
Secondary responses.
What is the main role of IgM?
Primary responses
What is the main role of IgA?
Protects mucosal surfaces
What is the main role of IgD?
Do not know.
What is the main role of IgG?
Allergy.
What immunogloblin class is present at very low levels?
E.
What is the main class of antibddy in serum?
G.
Further information on the structure of antibodies came from protein sequencing of which proteins?
Myeloma proteins.
Are the L chain types kappa and lambda class restricted?
No.
Are constant regions the same for a given H chain class or L chain type?
Yes.
What types of domains are antibodies comprised of?
Homologous domains.
How many amino acids comprise the immunogloblin domain?
110.
What is found in the immunogloblin domain allowing the structure to be compact?
Disulphide bridge.
The immunogloblin fold has a different amount of beta strands depending on whether it is in the C or V domain. How many beta strands are in the immungloblin fold when it is in the C and V domain respectively?
7 in the constant, 9 in the variable.
How many members are there in the Immunoglobulin gene superfamily in the human genome?
765 members.
What three things is the immunogloblin gene superfamily involved in?
Recognition, binding and adhesion.
How many hypervariable regions are in the variable regions of antibodies
3.
How long are hypervariable regions in antibodies?
7-12 amino acids.
What can hypervariable regions also be known as?
CDR’s (complementary determining regions).
The variable region in the antibodies are made up of two regions. What are these?
The hypervariable and the framework regions.
What type of interaction forms between the antibody and the antigens?
Non-covalent. These include electrostatic interactions, hydrogen bonds, VDW forces, hydrophobic interactions.
The non covalent interactions between an antibody and antigen are individually weak. When are they strong?
When many are formed simultaneously due to the site and the antigen containing complementary residues. This results in the antibody and antigen interaction being specific and at high affinity.
What do surface membrane immunogloblins contain?
26 hydrophobic amino acids at the C terminal.
What Ig classes can serve as B cell receptors?
All of them.
All classes of Ig can serve as B cell receptors. What two classes are mainly expressed by B cells?
M and D.
B cell receptors can recognize and bind to antigen. What can they not do?
Generate a signal.
What proteins are membrane bound immunoglobins also associated with?
Igalpha and Igbeta.
What do Igalpha and Igbeta contain?
A single ITAM
Where are the ITAMS in Igalpha and Igbeta
In the long cytoplasmic domains.
How do Ig alpha and Igbeta arrange themselves around the B cell receptor?
As alpha/beta dimer on either side.
